


Undergigantic

by FreddyFazbutt



Series: Undergigantic [1]
Category: Undertale (Video Game)
Genre: Adult Chara, Adult Frisk, Adult Monster Kid - Freeform, Alternate Universe - Canon Divergence, Chara Has Their Own Body, Chara and Frisk like to tease each other, F/F, F/M, Female Chara, Female Chara (Undertale), Female Frisk, Flowey is scared of humans, Frisk and Chara aren't themselves when they're hungry, Frisk and Chara like the taste of monsters in their mouth, Giant Chara, Giant Frisk, Humans are Giants, Humans have magic, Humiliation, LOVE and EXP is gained through eating monsters, Many Fetishes Of Mine, Monsters fear humans, Multi, No sex however, POV Frisk, POV Second Person, Socks are considered sexy by monsters, Sometimes Mute Frisk, Teasing, There are a skele-ton more monsters than normal, Though it isn't normal magic, Toriel thinks Frisk and Chara are gross, Vore, Weird and Confusing
Language: English
Status: In-Progress
Published: 2017-06-04
Updated: 2017-07-03
Packaged: 2018-11-09 03:14:46
Rating: Mature
Warnings: Graphic Depictions Of Violence, Major Character Death
Chapters: 8
Words: 3,475
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11095710
Author URL: https://archiveofourown.org/users/FreddyFazbutt/pseuds/FreddyFazbutt
Summary: This is not your Undertale story this is a Au where after the monster human war ended the humans sealed the monsters underground but not before stealing some of their magic the result was human souls becoming more powerful. Not only that but they grew to immense sizes over time and became able to use magic. Now two humans fall into the underground. What will happen next?





	1. Prologue

**Author's Note:**

> I do not own Undertale also this story while it might not have sex it does have vore and other fetish elements so be warned

It was a usual day in the underground.

Birds were singing.

Flowers were blooming.

On days like this 

everything should have been normal but the loud BANG! of something hitting the ground was a clear indication that everything was about to change...............


	2. Falling Falling FALLING!

**Summary for the Chapter:**

> You and Chara fall into the underground

Running.

Running.

Running.

That is what you and Chara were doing. You were running with your blood rushing in your ears and face. Behind you Chara was also running and the two of you ran until you both tripped over a vine and fell into a hole.

Now the two of you were FALLING Until you hit the ground with a resounding BOOM! The resulting shockwave shook the ground and you saw nothing but black. When you opened your eyes you were lying on the ground with Chara beside you.

You stood and shook Chara who replied "wha? what happened? last thing I remember we were running but I cannot remember why or what we were running from" You opened your mouth to speak but found yourself unable to speak and Chara said "oh great now you can't speak and where the hell are we?"

You just shrugged and pointed to the doors in front of you. A laugh came out of Chara as she said "You want to continue on? Fine but after we get home you better buy me a coffee" You nodded and the two of you began walking until you hit the doors which didn't look they were made for you or Chara because you both had to get on your knees and crawl through however you ended up getting your butt stuck in the door.

Your face blushed a shade of dark red as Chara said "Come on woman squeeze that big butt of yours through" she then gave you a little kick and you were pushed out with her following behind however you heard tiny squeaking from below you and you looked around for the source of the sound however you did not see anything and were going to continue but you felt something on your foot and you looked down expecting a bug but what you saw made you gasp.

It was a tiny flower smaller than your toe and it had a face. You think it must be trying to talk to you but you don't really care you just bend down and pick it up. Although it offers some struggle you easily pull it out of the ground and show it to Chara who simply snorts at your childish behaviour well until she sees its face.

She takes it from you and starts moving it around making you confused what is she doing? When you ask her she simply says she's examining it and she then licks it and lets out a "mmmm"

You give her a confused look and she simply hands you the flower who looks scared. You then lift the flower to your mouth and lick it and suddenly the most delicious flavour you've ever tasted floods your mouth. In fact it is so good you decide to keep the flower but not before knowing if it can talk so you set it on your shoulder and the first word it says is "Howdy!" you didn't respond and the flower continued with "My name is Flowey Flowey the Flower!"


	3. Meeting Toriel

**Summary for the Chapter:**

> You and Chara meet Toriel under very unusual circumstances

**Notes for the Chapter:**

> I cannot believe people are actually reading this. Oh well enjoy :)

You and Chara just stared at the flower on your shoulder for a moment before she burst into laughter over it's ridiculous name the flower looked slightly offended when she said "How'd you end up with a name like that one I mean that is bad really bad"

You smiled and picked him up off your shoulder and looked at Chara who said "Oh we have to put you somewhere for the time being" You weren't sure that is until Chara took him from you and proceeded to say "I wonder if Frisk has any room in her bra I mean I don't know how she keeps those mountains contained"

Your face turned incredibly red and just decided to put him in your pocket so you took him back and set him in your pocket. Just as you were about to keep going suddenly you felt a breeze down on your lower midriff.

You slowly looked down and gasped Chara had pulled down your shorts exposing your underwear not only that but behind you a woman you thought she was anyway was looking up at your exposed butt with a look of horror you quickly pulled your shorts back up but the damage was already done as the woman who looked like a goat said in a voice that sounded slightly disgusted "Greetings my children I am Toriel Caretaker of these Ruins I would like for you two to follow me I will show you around this place"

She departed with you and Chara who was still giggling at the stunt she pulled but you had a idea for a great revenge you waited until Toriel stopped at a spike puzzle and snuck up behind Chara pulling her shorts down and exposing her green and yellow underwear for the world to see.

Meanwhile Toriel's face had that disgusted look as Chara sent you a glare and pulled her shorts back up and you just laughed as Toriel explained the puzzle to you and Chara

"In order to do this one just press the switches I have labeled for you" but Chara just stepped over it however you were determined and solved the puzzle which made Toriel happy. She then led you to a room wth a dummy and proceeded to tell you "As humans living in the underground monsters may try to attack you if this happens talk to the dummy stall for time I will come to assist"

You giggled as you bent down to the dummy's level and said "Hey there Cutie" you seemed to have control over your voice and Toriel seemed happy.

Chara was smiling at you as Toriel said "if you wouldn't mind waiting here for me my children I have some things I have to do" She then left and Chara said " I guess we'll wait here" You were going to say something when both of your stomachs rumbled "Uh oh" Chara said 


	4. You might not be able to "stomach" this chapter (Vore chapter warning)

**Summary for the Chapter:**

> Warning this chapter contains graphic descriptions of blood and gore and vore so enjoy

You and Chara looked down at your growling stomachs and sighed. Chara said 'we haven't seen anything except monsters" you nodded and Chara said "Gotta eat monsters you know we do"

You nodded as the two of you began hunting for monsters and you saw a vegatable monster whch you picked up and opened your hungry maw. You heard whimpering as you dropped the vegetable monster into your mouth to be eaten.

Once inside you began chewing slowly after all you liked the flavour with every bite it bled congealed green magic which was slimy and smelt like blood CRUNCH! CRUNCH! CRUNCH! You heard screaming as you swallowed the chewed up monster and then it was gone meanwhile you watched as Chara picked up a jelly monster and swishses it around her mouth before swalloiwng it whole and burping out a cloud of white magic.

You grabbed a buglike monster and chewed on him your big chompers cutting his flesh until he was a chewed up pile of monster meat which you then swallowed with a 'squish'. The monsters were screaming and trying to run but you and Chara laughing at their pathetic attempts to escape picked up the whole group of monsters.

Chara said "Yay lets finish off with a shared meal" You nodded and you picked up a monster it was like a monster with horns and you stuck half of him in your mouth with Chara taking the other and then you pulled together which ripped the monster in half and left a white stain ffrom the monster blood all over your mouths.

You than let out a loud burp and put your palm of wriggiling monsters in your pocket leaving them in there for later Chara then let out all a huge burp as the two of you sat down to relax and digest your meal. You and Chara wiped your mouths and hands off in the water making you look like you hadn't just eaten monsters.

Finally you heard steps as Toriel made her way back to you her happy smile meaning that she ws happy you waited for her but little did she know as you let out a big burp which surprised her. She had no idea you had eaten some of her race.


	5. A fight with Toriel (Some buttcrush!)

**Summary for the Chapter:**

> You and Chara fight Toriel and learn of one of your magic powers

Toriel led you and Chara on to her house where she said welcome to your new home my children and she led you inside. Inside it was a nice tan color lit by lamps and Toriel then led you into a hallway where she procceeded to show the two of you into your new "room" but there was one problem both you and Chara were much too big.

In fact you both were on your hands and knees in the house so you knew neither of you could stay whih is why you asked Toriel "How do we leave the Ruins?" Toriel ignored you and asked "Would you both like to hear a snail fact? i have a book of them here"

You looked at Chara who said "Sure why not?" You looked back to Toriel and said "Sure" She smiled and read "There are 72 uses for snails how interesting right my children? You gave a 'yes' noise then said again "How do we leave the ruins" Toriel stood up and said quietly "Stay here I must go and do something"

 

You barely heard it from her since you both were so big but you did catch it and nodding to Chara who said "I guess we have to" and the two of you followed her down into the basement the tunnel seemed to be just your size and you and Chara were forced to crawl. All the while Toriel tried to convince you to go back but you were DETERMINED to succeed and finally the three of you stood at the door.

 

Toriel looked angry as she took a breath and said "You really wish to leave that badly? Fine then prove to me you are strong enough to survive" and flames erupted from her hands.

 

She then stood there but she looked confused for one second before hurling flames at you and you dodging them but then the unexpected happened Toriel began weaving through your legs which made dodging hard however as a result you accidently tripped over her and it all happened in the blink of a eye.

 

You were falling as Toriel who stood beneath you actually had fear in her face as your bum came down and crushed her making a 'splat' noise as your butt became covered in monster blood.

 

You began to cry as you liked Toriel and did not want to kill her then all of a sudden you were filled with DETERMINATION and time rewound backwards your left eye glowing red as your magic worked. You were standing back before you confronted Toriel with Chara saying "One of your abilities it seems"

 

You reapproached Toriel and before she could do anything you picked her up and gave her a kiss which made her look soften and she said "I'm sorry I don't have the right to keep you here as much as I want to but if I let you go you must promise me to never come back"

 

Your eyes full of tears you nodded and hugged her then set her down and turned to the door. 

Chara said "It seems that you'll be doing the majority of fighting from now on" You agreed and opened the door a bit and you realized you could feel cold resonating from the other side of the door. However you got a weird feeling like things were going to be different.


	6. This chapter is a great "feet" (Warning Feet Chapter)

**Summary for the Chapter:**

> You and Chara meet Sans and discover something weird about the monsters

**Notes for the Chapter:**

> Warning contains feet fetish scenes

You pulled open the doors and gasped at the sight before you. Chara said "whoa what the hell?" Before you lay a snow covered forest which seemed to stretch on for ages.

"Wow!" You said and Chara seemed to agree before you both began walking into the snowy expanse. You stopped not far from the door and said "Chara I think we should take off our shoes" She stopped and said "What why?" You responded "Our shoes aren't meant to be in the snow" Chara simply grumbled and said "FINE" and the two of you sat down and quickly popped your shoes off leaving your feet in just socks.

Chara asked "What am we even going to do with our shoes?" You thought for a second then said "Lets just discard them we are probably not going to need them anymore"

Chara just nodded and you both stood up and began walking again until you came to a bridge which was way too narrow for you to cross and you both stopped at the bridge. You heard crunching but when you looked down what you saw made you gasp.

It was a skeleton that seemed to be blushing a very dark shade of blue for some reason. You wriggled your toes because something told you to tease this strange skeleton with your feet so you wiggled your socked feet in front of the skeleton which made him blush bluer and made you laugh.

The skeleton still blushing finally said "I-i'm Sans Sans the Skeleton hey your humans right? Thats hilarious I'm a sentry hunting humans but I'm too lazy for that however my brother is a human hunting fanatic but don't worry about that just step over the bridge.You said "What's the matter Sans you look nervous" You wiggled your socked foot in the skeleton's face and Chara just laughed as you continued to embarass the skeleton with your foot then finally you stopped but just as you let the skeleton calm down.

You pulled your sock off and dropped it on him which made him say "Please stop" You giggled and said "Of course little bone boy but you can keep my sock as a gift" He gulped before saying" Really?"

You nodded but Chara intervened and said "Frisk stop flirting with him he's probably annoyed you threw your stinky sock on him" You apolgized and took back your sock and put it back on your foot and Sans looked like he would rather be anywhere than here as you continued on.


	7. Meeting Papyrus

**Summary for the Chapter:**

> You and Chara meet Papyrus and a still very embarassed Sans

**Notes for the Chapter:**

> Glad so many people have read this story

You continued into the next area with Chara following behind you and observed as Sans who was also following said "I have a brother Papyrus he's going to try to capture you"  

You burst into laughter and said "Oh Sansy we'll just wiggle our socks and he won't even Chara" The pun you made had Sans chuckle and Chara groan. You stopped at a area that you thought was Sans sentry station which after he said "This is my sentry station wait here my bro should be coming any minute"

So you nodded to Chara and the both of you sat down with you sitting on opposite sides of each other with Sans trapped in the middle with both of your dirty socks and he turned so blue you thought he would explode.

Suddenly you heard a loud voice say "SANS WHAT ARE YOU DOING YOU'RE SUPPOSED TO BE DOING YOUR PUZZLES" and a skeleton walked into the circle you and Chara created which made you giggle as he didn't even notice the two of you.

He said "WHY DOES YOUR STATION SMELL LIKE DIRTY SOCKS SANS?" Sans merely said "look behind you" and he did with a gasp he looked at you and then Chara and said "WOWIE GIANT HUMANS" Chara said "Actually my dear Papyrus we are average size for humans" That made both of the skeletons gasp. Sans said "Really?" You nodded.

Papyrus then said "SO THE REASON FOR THE SMELL IS YOUR SOCKS ISN'T IT" You nodded which made him blush a bright orange. You and Chara stood up and Papyrus said "I WAS GOING TO DO SOME PUZZLES BUT THE TWO OF YOU ARE MUCH TOO BIG FOR THEM SO I GUESS I CAN'T REALLY STOP YOU BUT I WAS WONDERING IF YOU'D TAKE MY BROTHER WITH YOU" You were taken aback and said "sure" Sans said "Why bro?"

Papyrus said "I KNOW ABOUT THE SOULS SANS AND IF THESE HUMANS ARE RIGHT IT MEANS THAT WE WILL NOT STAND EVEN A LITTLE CHANCE AGAINST THE HUMANS SO I WANT YOU TO GO WITH THEM SO YOU CAN TELL ASGORE NOT TO TAKE ANY MORE SOULS"

You and Chara gasped as Sans nodded and waited for you to pick him up. You bent down and picked up the itty bitty skeleton then winked to Chara as you opened your sweater and placed Sans so he could see but he was stuck between your breasts. "There Comfy?" you said as the skeleton was blue all over. He said "y-y-yes very warm in here"

You and Chara continued until you reached the end of the forest and found yourselves in a cozy little town called Snowdin. You were too big to do anything so you asked Sans to go and find some food for the road. Which after a few minutes he came back carrying burgers and fries in a bag but you said "Sans that's barely a morsel for me how is there going to be enough for Chara and you?"

He said "These burgers fill anyone's stomach up even humans like you two" You said "whoa sweet" You put Sans back in his position and continued walking until you were stopped by Papyrus who said HUMANS AND SANS WOULD YOU LIKE TO HAVE A QUICK HANG OUT BEFORE YOU GO?".


	8. Hanging out with Papyrus and exploring Waterfall

**Summary for the Chapter:**

> You hang out with Papyrus and begin exploring waterfall with Sans

**Notes for the Chapter:**

> The thought of getting another chapter fills you with DETERMINATION

Chara said "Sure we'd love that Papyrus" and you set Sans down on the ground as you sat down with Chara following suit. Papyrus laughed a hearty "NYHEHEHE!" and said "SO THE GREAT PAPYRUS HAS MADE SOME SPAGHETTI FOR OUR HANGOUT!

You smiled as he set down a tiny bowl of spaghetti which you said "Dear Papyrus me and Chara are way too big for that" Papyrus gasped and said "YOU'RE RIGHT HUMAN" and he actually pulled out a bowl of spaghetti your size somehow.

You and Chara gasped at the size of the bowl of spaghetti before you snatched the bowl quickly out of Papyrus's hands and you and Chara devoured the whole thing easily. You both burped rubbing your tummies as Papyrus said "WELL IT SEEMS YOU ENJOY MY SPAGHETTI HUMANS" you nodded while Chara said "I've never been this full in my life"

Papyrus smiled brightly and said "I KNEW IT! THE GREAT PAPYRUS HAS SUCCEEDED ONCE AGAIN NYHEHEHE!" You giggled and picked up Papyrus while Chara picked up Sans and you pecked Papyrus on the forehead while Chara pecked Sans on the cheek making them both blush.

You stood nodding to Chara who stood with Sans in her palm still as she said "anyways it's time we went" Papyrus smiled and said "GOOD LUCK HUMANS AND GOODBYE" You waved goodbye to Papyrus and started walking.

After a few hours you had arrived at what Sans called Waterfall being giant you could see the place in all it's glory as you, Chara and Sans took a break at the waterfall which was more like a stream to you and Chara.

You sat down your big butt blocking the waterfall while Chara sat in the tunnel blocking the way with her big butt  while Sans sat in between you as he pulled the spaghetti he had mentioned earlier from his pockets.

You and Chara looked skeptically at it as you both took the tiny bowl of spaghetti and stared at it. You were the first to pick up a noodle and take a bite as you suddenly felt really full. You said to Chara "He was right I feel full" Chara ate a noodle and said "I can't believe it but he was right"

Sans just smiled and was gonna reply but was interrupted by the sound of magic being activated. You and Chara quickly pretended to be part of the background as a heavily armored monster walked up to Sans and asked "SANS! WHERE'S THE HUMANS?"

Sans shrugged and said "who's this Hugh Man guy you're talkin bout? you giggled and Chara groaned as the armored monster said "SANS THIS IS NO TIME FOR JOKES WHERE ARE THEY?" Sans shrugged as the armored monster growled "GRAHH! YOU'RE USELESS I'LL LOOK SOMEWHERE ELSE!" and stormed off.

You asked "Who was that?" Sans replied "Oh that was just Undyne captain of the royal guard kinda looking for humans like you two" Chara said "Oh great well I guess it is what it is"


End file.
